The present invention relates to a voltage level shifter and, more particularly, to a voltage level shifter for shifting signal levels from a low voltage level to a higher voltage level.
Integrated circuits typically have peripheral or input/output (I/O) circuitry and internal core circuitry. The internal core circuitry often performs various processing-specific functions as fast as possible with minimal power consumption. As a result, power supply voltages that are used to power the core circuitry have been getting smaller. The I/O circuitry drives or provides signals from the core to external circuits at a specified signal power and voltage levels. The I/O circuitry also is frequently required to interface with various interface standards.
In view of the above, there is a need for high-speed, point-to-point interface communications between lower supply voltage chip level core circuitry signals, e.g., around 1 Volt (V) or less, and external circuits operating at higher voltage levels (e.g., 2.5V, 3.3V, or higher). Also, many systems, and even internal core circuitry, are designed with a variety of technologies operating at multiple voltage levels. It has also been found to be very challenging to provide level shifting circuits and output buffer circuits that interface multiple voltage levels while operating at the desired limits of the I/O speed and power consumption. It would therefore be desirable if a level shifter circuit could be implemented that can provide relatively high speed voltage output transitions without requiring relatively high levels of power consumption.